The death of a 31-year old man after his vehicle went through the ice in Mississippi Lake in Ontario’s Lanark County in January is an unfortunate reminder that venturing out on frozen lakes and rivers is a risky business. Some of us do it because we have to, on ice roads. Many of us do it because we want to, as part of our winter recreation. Ice is never totally safe, but the more you know, the less chance you have of losing a vehicle—or your life.
1. The gold standard for ice safety is clear or “blue” ice. It’s the basis for recommended minimum thicknesses. “White” or snow ice is the mix of snow and ice that forms on top of clear ice, and should be considered half as thick as it is when figuring out load bearing. If there’s a mix of blue and white ice, you have to calculate each part separately. Four inches of white ice on top of four inches of blue ice has the load-bearing equivalent of six inches of blue ice.
2. The Canadian government’s guidelines for ice bridge construction say a general rule of thumb is “one inch (2.5 cm) of clear blue ice for every thousand pounds (450 kg),” but says no ice less than six inches thick should be used by vehicles.
3. Because Minnesota is mad about ice fishing, its Department of Natural Resources has some of the best advice around on ice safety. DNR says to stay off any ice less than four inches thick. Four inches of clear blue ice are OK for ice fishing or other activities on foot, five to seven inches for snowmobiles and ATVS, eight to twelve inches for a car or small pickup, and twelve to fifteen inches for a medium truck.
4. Alberta’s Workplace Health and Safety Guidelines provide detailed recommended minimum thickness for travel on clear ice. For one person on foot, it’s 50 millimeters for a lake, 60 for a river. For a group in single file, it’s 80 mm for a lake, 90 for a river. A passenger car (2,000 kg) needs 180 mm for a lake, 210 for a river. A light truck (2,500 kg) needs 200 mm for a lake, 230 for a river. A medium truck (3,500 kg) needs 260 mm for a lake, 300 mm for a river.
5. If you’re travelling in a group, stay well spaced. Alberta’s Workplace Health and Safety Guidelines say the distance between vehicles should be 100 times the minimum applicable ice thickness. So a car on a lake, needing a minimum 180 mm of ice, should stay 18 meters behind another vehicle. Canada’s ice bridge guidelines warn that if a vehicle in a convoy is going to go through, it’s probably going to be the second one, not the first.
6. Ice flexes and recovers after a vehicle passes over it, but a parked vehicle delivers a constant load that can cause failure. Canada’s ice bridge guidelines say ice should be considered effectively half as thick if a vehicle is parked on it. Minnesota’s DNR says cars, trucks and SUVs should be parked at least 50 feet apart and moved every two hours. Drill a hole beside each vehicle and watch for water welling up, which is a sign the ice is deflecting downwards.
7. Minnesota’s DNR recommends checking ice thickness every 150 feet if you’re going to travel over it. Canada’s ice road guidelines are more conservative, saying every 50 feet with rivers and 100 feet with lakes. You can use a variety of tools to poke a hole in the ice. A handy one Minnesota’s DNR recommends is a cordless drill with a 5/8 inch wood auger bit on a long shaft. It will make a hole big enough to insert a tape measure.
8. Some people think driving faster on ice is safer, presumably because they’ll be making their escape from any ice that is failing. In fact, driving fast is more dangerous, as it sets up a pressure wave in the ice that can cause it to fracture. Alberta’s Workplace Health and Safety Guidelines advise keeping speed below thirty kilometres an hour on open ice with water depths of less than 15 meters, and fifteen kilometres and hour when approaching shore or travelling parallel and close to shore.
9. If you’re going to be driving on ice, be prepared for the worst. Vehicles should have windows rolled down for a quick escape. ATV and snowmobile operators can wear an inflatable PFD under their winter clothes, but DON’T do this in a car or truck. If the vehicle goes through the ice and the PFD inflates, you might not get out of it.